With reference to FIGS. 7-9, a conventional injection head structure of a die casting machine contains a base 40 with a third inlet 401, a sleeve 50, and a nozzle tube (not shown).
The base 40 also includes a through hole 402 defined at a central portion thereof, a head block 41 extending outwardly from the outer wall thereof opposite to the first inlet 411 and having an outlet 411 formed in the head block 41, and a neck 42 connected with the head block 41 and the base 40 and having a guiding hole 421 defined in the neck 42 and communicating with the through hole 402 and the outlet 411, two opposite fixing extensions 43 extending outwardly from a top end thereof so as to fix the base 40 at a predetermined position of a die casting machine (not shown).
The sleeve 50 is mounted in the through hole 402 of the base 40 and includes a receiving groove 51 defined at a center thereof and a fourth inlet 52 formed on an outer wall thereof and corresponding to and communicating with the third inlet 52 of the base 40, and a feeding orifice 53 arranged on a bottom end of the outer wall thereof and communicating with the guiding hole 421.
The nozzle tube (not shown) is fixed in the outlet 411 of the base 40.
It is to be noted that an outer diameter of the sleeve 50 and an inner diameter of the through hole 402 of the base 40 are worked at higher precision so as to obtain accurate perpendicularity and roundness, thus connecting the plunger and the base together accurately.
In other words, the through hole 402 of the base 40 is bored and is expended at 850° C., thereafter the plunger 50 is put into the through hole 402 of the base 40 and is cooled over 24 hours so that the plunger 50 is connected with the base 40 tightly.
But such a conventional injection head structure has the following advantages:
1. The sleeve 50 and the base 40 are worked at high-temperature heat treatment, thus having high working cost. The through hole 402 of the base 40 is bored at 850° C., an unsafe working process occurs accordingly.
2. The sleeve 50 cannot be removed from the base 40, so the injection head is replaced at high cost. Furthermore, the through hole 402 of the base 40 deforms easily in heating and cooling process, a gap B therefore forms between the outer diameter of the sleeve 50 and the inner diameter of the through hole 402 as shown in FIG. 8. When the injection head is soaked in a metal fluid tank 60 at high temperature, and a hydraulic cylinder 70 pushes metal fluid in the receiving groove 51 so that the metal fluid is injected out of the outlet 411 of the base 40 from the feeding orifice 53 via the guiding hole 421, hence the metal fluid leaks from the gap B and cooled to form wastes C (as illustrated in FIGS. 9 and 10), such that the sleeve 50 is connected with the base 40 by ways of the wastes C. The sleeve 50 cannot be removed from the through hole 402 of the base 40, so the injection head has to be replaced completely after a period of using time.
3. The sleeve 50 is made of SKD61 steel, so when it is placed in the through hole 402 of the base 40, decarbonization generates between the through hole 402 and an inner wall of the receiving groove 51, and the inner wall of the receiving groove 51 of the sleeve 50 is ground, thus increasing working cost.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.